Methods and apparatus for sorting and/or depositing nanotubes

ABSTRACT

Methods and apparatus for forming devices using nanotubes. In one embodiment, an apparatus for depositing nanotubes onto a workpiece comprises a vessel configured to contain a deposition fluid having a plurality of nanotubes including first nanotubes having a first characteristic and second nanotubes having a second characteristic. The apparatus further includes a sorting unit in the vessel configured to selectively isolate or otherwise sort the first nanotubes from the second nanotubes, and a field unit in the vessel configured to attach the first nanotubes to the workpiece. For example, the field unit can attach the first nanotubes to the workpiece such that the first nanotubes are at least generally parallel to each other and in a desired orientation relative to the workpiece.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/877,874, filed Sep. 8, 2010, now U.S. Pat. No. 8,377,281, which is adivisional of U.S. application Ser. No. 11/217,170, filed Sep. 1, 2005,now U.S. Pat. No. 7,799,196, each of which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present invention relates to methods and apparatus for sortingnanotubes and/or depositing nanotubes onto microfeature workpieces.Several embodiments of the invention are directed towardelectrochemically depositing nanotubes in a desired arrangement relativeto each other and/or a workpiece.

BACKGROUND

Nanotubes have one or more sheet-like matrices of carbon atomsconfigured into cylinders having one or more walls. Different types ofnanotubes can have different properties. For example, nanotubes can beconductive, dielectric, or semiconductive. Nanotubes can accordingly betransistors, emitters, interconnects, or other components used in memorydevices, displays, or other products. One challenge of using nanotubesis depositing the desired type of nanotubes onto a workpiece so that thenanotubes are in a desired configuration.

One process for depositing nanotubes onto a workpiece is to suspend thenanotubes in a solution, immerse the workpiece in the solution, and thenremove the workpiece. After the workpiece is removed from the solution,the liquid evaporates and the nanotubes remain on the surface of theworkpiece. The surface of the workpiece can have hydrophilic regionswhere the solution preferentially remains on the workpiece surface afterremoving the workpiece from the solution to deposit the nanotubes onlyon the hydrophilic regions. One drawback of this process is that thenanotubes are typically in a random configuration on the workpiece.Another problem with this process is that all the different types ofnanotubes in the solution are typically deposited onto the surface ofthe workpiece. As such, this process may not provide the desiredarrangement and/or types of nanotubes on a workpiece.

Chemical Vapor Deposition (CVD) processes similar to those used todeposit materials in the fabrication of semiconductor devices can beused to deposit nanotubes. CVD processes, however, also typicallydeposit the nanotubes in a random configuration. As such, one drawbackof this process is that the nanotubes may not be arranged in the desiredconfiguration on the workpiece.

Still another process for depositing nanotubes is to electroplate thenanotubes onto a workpiece. One such process immerses a workpiece in anelectrolyte having a plurality of nanotubes and establishes anelectrical field between the workpiece and a counter-electrode. Theelectrical field attaches the nanotubes to the workpiece such that thenanotubes are generally parallel to the direction of the electricalfield. As a result, the nanotubes are typically parallel to each otherand perpendicular to the workpiece. Although electroplating nanotubesonto workpieces can arrange the nanotubes in a desired configuration(e.g., parallel to each other), different types of nanotubes in aplating solution are generally plated onto the workpiece. As a result,undesired nanotubes may be deposited onto the workpiece along withdesired nanotubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a process for depositingnanotubes onto a workpiece in accordance with an embodiment of theinvention.

FIG. 2 is a schematic view illustrating a process for depositingnanotubes onto a workpiece in accordance with another embodiment of theinvention.

FIG. 3 is a schematic view illustrating a process for depositingnanotubes onto a workpiece in accordance with still another embodimentof the invention.

FIG. 4 is a schematic view illustrating a process for depositingnanotubes onto a workpiece in accordance with yet another embodiment ofthe invention.

FIG. 5 is a schematic view illustrating a method for depositingnanotubes onto a workpiece in accordance with another embodiment of theinvention.

DETAILED DESCRIPTION

A. Overview

The present invention is related to methods and apparatus for formingcomponents using nanotubes. Several embodiments of the invention aredirected toward sorting nanotubes so that selected nanotubes aredeposited onto a workpiece. Other embodiments of the invention aredirected toward controlling the alignment or other arrangement of thenanotubes on the workpiece. These different embodiments can also becombined such that the nanotubes are sorted and then deposited onto amicrofeature workpiece in a desired configuration. As a result, severalembodiments of the invention are expected to enable the fabrication ofconductive lines, memory cells, emitters, transistors, interconnects,and other components in which it is desirable to deposit certain typesof nanotubes in precise arrangements.

One embodiment of a method for depositing nanotubes onto a workpieceincludes contacting a surface of the workpiece with a deposition fluidcontaining a plurality of nanotubes. This method continues by separatinga first portion of the nanotubes from a second portion of the nanotubesin the deposition fluid, and establishing an electrical field betweenthe surface of the workpiece and a counter-electrode in the depositionfluid. The electrical field electrochemically deposits at least one ofthe first portion of the nanotubes and/or the second portion of thenanotubes onto the workpiece.

Another method of depositing nanotubes onto a workpiece uses adeposition fluid containing first nanotubes having a firstcharacteristic and second nanotubes having a second characteristic. Thismethod comprises separating the first nanotubes from the secondnanotubes, and electrochemically depositing the first nanotubes onto theworkpiece. For example, the first nanotubes can be electrochemicallydeposited onto the workpiece by establishing an electrical field in thedeposition fluid that drives the first nanotubes to the workpiece.

Yet another embodiment of a method for depositing nanotubes onto aworkpiece comprises providing a deposition fluid containing firstnanotubes having a first characteristic and second nanotubes having asecond characteristic. This method further includes isolating the firstnanotubes from the second nanotubes in the deposition fluid, andarranging the first nanotubes on the workpiece. The first nanotubes arearranged on the workpiece such that they are at least generally parallelto each other and in a desired orientation relative to the workpiece.

Another aspect of the invention is directed toward an apparatus fordepositing nanotubes onto a workpiece. One embodiment of such anapparatus includes a vessel configured to contain a deposition solutionhaving a plurality of nanotubes, a workpiece holder configured to hold asurface of the workpiece in a deposition zone relative to the vessel,and a counter-electrode in the vessel. The workpiece holder has at leastone electrical contact configured to provide an electrical potential tothe workpiece such that the workpiece defines another electrode. As aresult, when the processing solution is in the vessel, an electricalbias can be applied to the workpiece and the counter-electrode toestablish an electrical field in the deposition solution. Thisembodiment of the apparatus further includes a nanotube separator in thevessel configured to sort a first portion of the nanotubes from a secondportion of the nanotubes.

Another embodiment of an apparatus for depositing nanotubes onto aworkpiece in accordance with the invention comprises a vessel configuredto contain a deposition fluid having a plurality of nanotubes includingfirst nanotubes having a first characteristic and second nanotubeshaving a second characteristic. The apparatus further includes a sortingunit in the vessel configured to selectively isolate the first nanotubesfrom the second nanotubes and a field unit in the vessel configured toattach the first nanotubes to the workpiece such that the firstnanotubes are at least generally parallel to each other and in a desiredorientation relative to the workpiece.

Another embodiment of an apparatus for depositing nanotubes onto aworkpiece in accordance with the invention comprises a vessel configuredto contain a deposition solution having a plurality of nanotubes andmeans for isolating a first portion of the nanotubes from a secondportion of the nanotubes. The apparatus further includes means forelectrochemically attaching the first portion of the nanotubes to theworkpiece such that the nanotubes are at least generally parallel toeach other and in a desired orientation relative to the workpiece.

FIGS. 1-5 illustrate several embodiments of methods and apparatus forsorting nanotubes and/or depositing nanotubes onto microfeatureworkpieces in a desired arrangement in accordance with variousembodiments of the invention. Specific details of the invention are setforth in the following description and in FIGS. 1-5 to provide athorough understanding of these embodiments of the invention. Oneskilled in the art, however, will understand that the present inventionmay have additional embodiments, or that other embodiments of theinvention may be practiced without several of the specific featuresexplained in the following description. The term “microfeatureworkpiece” is used throughout to include substrates upon which and/or inwhich microelectronic devices, micromechanical devices, data storageelements, optics, and other features are fabricated. For example,microfeature workpieces can be semiconductor wafers, glass substrates,dielectric substrates, or many other types of substrates. Many featureson such microfeature workpieces have critical dimensions less than orequal to 1 μm, and in many applications the critical dimensions of thesmaller features are less than 0.25 μm or even less than 0.1 μm.Furthermore, the terms “planarization” and “planarizing” mean forming aplanar surface, forming a smooth surface (e.g., “polishing”), orotherwise removing materials from workpieces. Where the context permits,singular or plural terms may include the plural or singular terms,respectively. Moreover, unless the word “or” is expressly limited tomean only a single item exclusive from other items in reference to alist of at least two items, then the use of “or” in such a list is to beinterpreted as including (a) any single item in a list, (b) all theitems in the list, or (c) any combination of the items in the list.Additionally, the term “comprising” is used throughout to mean includingat least the recited feature(s) such that any greater number of the samefeatures and/or types of other features and components are notprecluded.

B. Sorting and/or Depositing Nanotubes

FIG. 1 is a schematic view illustrating an apparatus 10 for depositingnanotubes onto a workpiece 12 in accordance with an embodiment of theinvention. In this embodiment, the apparatus 10 includes a vessel 20configured to contain a deposition fluid, such as a solution 22 having aplurality of nanotubes 24. The deposition fluid can be a liquid solutionfor electrochemically depositing the nanotubes 24 onto the workpiece 12,and in this case the vessel 20 can be a fountain plater similar to thesingle-wafer fountain platers manufactured by Semitool, Inc. In otherembodiments, the deposition fluid can be a gaseous solution containingthe nanotubes 24, and in this case the vessel 20 can be configured intoa vapor deposition chamber.

The apparatus 10 further includes a workpiece holder 30 having at leastone electrical contact 32 configured to engage a surface of theworkpiece 12, a counter-electrode 40 in the vessel 20, and a powersupply 50 operatively coupled to the workpiece holder 30 and thecounter-electrode 40. In operation the power supply 50 applies anelectrical bias to the surface of the workpiece 12 and thecounter-electrode 40 for generating an electrical field in the solution22 that attaches the nanotubes 24 to the surface of the workpiece 12.

The apparatus 10 in the embodiment illustrated in FIG. 1 furtherincludes a sorting unit 60 for sorting the nanotubes 24. The sortingunit 60 can be configured to sort a first portion of the nanotubes 24from a second portion of the nanotubes 24 so that the desired nanotubesare deposited onto the workpiece 12. The sorting unit 60, for example,can be a separator that separates first nanotubes from second nanotubes.The first and second nanotubes can have different electrical properties(e.g., conductive, dielectric, semiconductive), magnetic properties,size, mass, and/or other characteristics that can distinguish the firstnanotubes from the second nanotubes. For example, the first nanotubescan be single-walled nanotubes and the second nanotubes can bemulti-walled nanotubes. In another example, the first nanotubes can bemetallic and the second nanotubes can be dielectric or semiconductive,or the first nanotubes can be magnetic and the second nanotubes can benonmagnetic. The sorting unit 60 can mechanically sort the first andsecond nanotubes from each other, or the sorting unit 60 canelectrically and/or magnetically separate the first and second nanotubesfrom each other in addition to or in lieu of mechanical sorting. Thesorting unit 60 is accordingly configured to preferentially isolate thefirst or second nanotubes from each other to selectively deposit one ofthe first or second nanotubes onto the workpiece 12.

The sorting unit 60 in the embodiment of the apparatus 10 illustrated inFIG. 1 can be a filter that filters out larger nanotubes to isolatesmaller nanotubes for deposition onto the workpiece 12. The filter, forexample, can be a mesh or a plate with holes in it that allows thedesired size of nanotubes to pass through the filter for depositing onlythe smaller nanotubes onto the workpiece 12. It is expected that theembodiment of the sorting unit 60 illustrated in FIG. 1 is particularlyuseful for separating smaller diameter nanotubes (e.g., single-wallednanotubes) from larger diameter nanotubes (e.g., multi-wallednanotubes). The sorting unit 60 can also pre-align the nanotubesrelative to the workpiece 12. The electrical field and the sorting unit60 can accordingly operate together to deposit the nanotubes in adesired configuration. For example, the electrical field and the sortingunit 60 can operate together to arrange the nanotubes on the workpiecesuch that the nanotubes are at least generally parallel to each otherand in a desired orientation relative to the surface of the workpiece12.

The particular embodiment of the apparatus 10 shown in FIG. 1 operatesby flowing the solution 22 through the vessel 20 such that the nanotubes24 pass through the sorting unit 60. As explained above, the sortingunit 60 separates desired nanotubes from undesired nanotubes andpre-aligns the nanotubes 24 for plating onto the workpiece 12. Theworkpiece holder 30 holds the workpiece 12 in the solution 22, and thepower supply 50 applies an electrical bias to the workpiece 12 and thecounter-electrode 40 to generate the electrical field in the solution22. The electrical field accordingly causes the nanotubes proximate tothe surface of the workpiece 12 to become attached to the workpiece 12.In other embodiments, the workpiece 12 and counter-electrode 40 can beorientated vertically instead of horizontally. In still additionalembodiments, the solution can be stagnant or stationary, and thenanotubes can move through the solution under the influence of gravity,an electrical field, a magnetic field, and/or an electromagnetic field.

One expected advantage of the apparatus 10 is that the sorting unit 60sorts the nanotubes in a manner such that the desired types of nanotubesare deposited onto the workpiece 12. The sorting unit 60 can furtherpre-align the nanotubes so that they are in a better orientation to bearranged perpendicular to each other and at a desired angle relative tothe surface of the workpiece 12. Another advantage of the apparatus 10is that the electrical field further aligns the nanotubes relative toeach other and causes the nanotubes to be attached to the surface of theworkpiece 12 in a desired arrangement. As a result, several embodimentsof the apparatus 10 are expected to provide controlled deposition ofnanotubes for manufacturing transistors, interconnects, emitters, orother components in electrical and/or mechanical devices.

FIG. 2 is a schematic view illustrating an apparatus 10 a for sortingand depositing nanotubes onto microfeature workpieces in accordance withanother embodiment of the invention. The apparatus 10 illustrated inFIG. 1 is similar to the apparatus 10 a illustrated in FIG. 2, and thuslike referenced numbers refer to like components in FIGS. 1 and 2. Inone embodiment, the apparatus 10 a includes a sorting unit 60 a having afilter 62 and a mask 64. The filter 62 can be a mesh or another type offilter that separates first nanotubes from second nanotubes as describedabove. The mask 64 can be a plate or other member having a plurality ofopenings 66 through which the nanotubes can be deposited onto selectedareas of the workpiece 12. For example, the mask 64 can include apattern of openings 66 corresponding to the pattern of the array areason the workpiece 12 to shield the peripheral regions on the workpiece 12from the nanotubes. The sorting unit 60 a is generally placed close tothe workpiece 12 so that the openings 66 in the mask 64 are aligned withthe desired areas of the workpiece 12. In operation, the desirednanotubes are driven through the filter 62 and through the openings 66to be electrochemically deposited onto the surface of the workpiece 12.

In an alternative embodiment of the apparatus 10 a shown in FIG. 2, thesorting unit 60 a includes only the mask 64 (i.e., does not include thefilter 62). In this embodiment, the mask 64 separates a first portion ofthe nanotubes from a second portion of the nanotubes by allowing onlythe portion of the nanotubes aligned with the openings 66 to bedeposited onto the workpiece 12. As a result, the functionality of thesorting units is not limited to filtering one type of nanotube fromanother, but can alternatively include separating the same type ofnanotubes from each other for selective deposition on desired areas of aworkpiece.

FIG. 3 is a schematic view illustrating an apparatus 10 b for depositingcarbon nanotubes onto a workpiece in accordance with another embodimentof the invention. The apparatus 10 b is similar to the apparatus 10 and10 a illustrated in FIGS. 1 and 2, and thus like reference numbers referto like components in FIGS. 1-3. The apparatus 10 b includes a solution22 b having nanotubes 24 that have been functionalized by adding one ormore functional molecules 26 (shown schematically) to the nanotubes 24.The functional molecules 26 have a specific property to (a) furtherfacilitate the alignment of the nanotubes 24 to an electrical orelectromagnetic field in the solution 22 b and/or (b) further facilitatesorting a first type of nanotube from a second type of nanotube. Thefunctional molecules 26 can impart a desired electrical property,chemical property, magnetic property, mass, size, density, or othercharacteristic to the nanotubes 24. The functional molecules 26 canpreferentially or selectively functionalize different types of nanotubes(e.g., metallic, insulating, etc.) because of the different chemicalinteraction between the functional molecules 26 and the different typesof nanotubes. For example, the nanotubes 24 can be functionalized with asuitable functional molecule 26 to provide a dipole structure thatfurther enhances the orientation of the carbon nanotubes in the fieldbetween the workpiece 12 and the counter-electrode 40. The apparatus 10b can optionally include a sorting unit 60 b for separating a firstportion of the nanotubes from a second portion of the nanotubes. Theoptional sorting unit 60 b can be one of the sorting units 60 or 60 adescribed above with reference to FIGS. 1 and 2, or any of the othersorting units described below with reference to other embodiments of theinvention.

FIG. 4 is a schematic view of an apparatus 100 for sorting anddepositing carbon nanotubes onto microfeature workpieces in accordancewith another embodiment of the invention. In this embodiment, theapparatus 100 includes a vessel 120 having a sorting zone 122 a and adeposition zone 122 b. The vessel 120 is configured to direct a flow Fof the solution 22 through the sorting zone 122 a and the depositionzone 122 b. As explained in more detail below, the apparatus 100 sorts afirst type of nanotube from a second type of nanotube in the sortingzone 122 a, and then deposits the selected type of nanotube onto theworkpiece 12 in the deposition zone 122 b.

The apparatus 100 can further include a sorting unit 160 in the sortingzone 122 a. In this embodiment, the sorting unit 160 is a fieldgenerator having a first element 162 a and a second element 162 b thatgenerate a sorting field S transverse to the flow F of the solution 22in the sorting zone 122 a. The first and second elements 162 a and 162 bcan be opposite poles of magnets, opposing electrodes, orelectromagnets. The sorting unit 160 preferentially separates firstnanotubes 24 a from second nanotubes 24 b such that the second nanotubes24 b generally remain in the sorting zone 122 a and the first nanotubes24 a generally pass to the deposition zone 122 b. As explained abovewith reference to FIG. 3, the nanotubes 24 a and 24 b can befunctionalized such that the sorting unit 160 preferentially separatesthe second nanotubes 24 b from the first nanotubes 24 a using theseparation field S. The sorting unit 160 can further include amechanical separator 164, such as a filter, to further sort thenanotubes passing to the deposition zone 122 b.

The apparatus 100 further includes a workpiece holder 130 that can bepositioned in the deposition zone 122 b and a counter-electrode 40 inthe deposition zone 122 b. The power supply 50 is operatively coupled tothe workpiece holder 130 and the counter-electrode 40 to apply a firstelectrical potential to the workpiece 12 via the workpiece holder 130and a second electrical potential to the counter-electrode 40 forestablishing a deposition field D in the deposition zone 122 b. As aresult, the first nanotubes 24 a in the deposition zone 122 b aredeposited onto the surface of the workpiece 12.

FIG. 5 is a schematic view illustrating an apparatus 200 for sorting anddepositing nanotubes onto microfeature workpieces in accordance withstill another embodiment of the invention. In this embodiment, theapparatus 200 includes a vessel 220 having a sorting zone 222 a, adeposition zone 222 b separate from the sorting zone 222 a, and aconduit 223 between the sorting zone 222 a and the deposition zone 222b. The apparatus 200 also includes a sorting unit 260 in the sortingzone 222 a for separating first nanotubes 24 a from second nanotubes 24b. The sorting unit 260 can be a field generator having one or moreelements for generating an electrical field, a magnetic field, or anelectromagnetic field. The sorting unit 260, for example, can be anelectromagnet or permanent magnet that selectively attracts the secondtype of nanotubes 24 b in the solution 22. The sorting unit 260 canfurther include a filter or other type of mechanical separator 264 tofurther enhance the sorting of the nanotubes. The sorting unit 260 canalternatively be a catch basin that catches heavier or higher densitynanotubes. The apparatus 200 can further include a workpiece holder 30,a counter-electrode 40, and a power supply 50 as described above withreference to FIG. 1. In operation, therefore, the sorting unit 260separates a first portion of the nanotubes 24 a from a second portion ofthe nanotubes 24 b in the sorting zone 222 a, and the power supply 50generates a deposition field in the deposition zone 222 b for depositingthe desired nanotubes onto the surface of the workpiece 12.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. For example, features and componentsof the apparatus shown in FIGS. 1-5 can be combined with each other inadditional embodiments. Additionally, the workpiece holder andcounter-electrode arrangements can be vertical or horizontal in thevarious embodiments. Accordingly, the invention is not limited except asby the appended claims.

I claim:
 1. A method of depositing nanotubes onto a workpiece,comprising: providing a deposition fluid containing first nanotubeshaving a first characteristic and second nanotubes having a secondcharacteristic; isolating the first nanotubes from the second nanotubesin the deposition fluid; and arranging the first nanotubes on theworkpiece such that the first nanotubes are at least generally parallelto each other and in a desired orientation relative to the workpiece. 2.The method of claim 1 wherein isolating the first nanotubes from thesecond nanotubes comprises filtering the second nanotubes from the firstnanotubes.
 3. The method of claim 1 wherein isolating the firstnanotubes from the second nanotubes comprises sorting the firstnanotubes from the second nanotubes in the deposition fluid.
 4. Themethod of claim 3 wherein sorting the first nanotubes from the secondnanotubes comprises passing the first nanotubes through a mesh thatfilters out the second nanotubes.
 5. The method of claim 3 whereinsorting the first nanotubes from the second nanotubes comprises applyingan energy field to the deposition fluid that acts on the secondnanotubes differently than the first nanotubes.
 6. The method of claim 1wherein arranging the first nanotubes on the workpiece compriseselectrochemically depositing the first nanotubes onto the workpiece. 7.The method of claim 6 wherein electrochemically depositing the firstnanotubes onto the workpiece comprises establishing an electrical fieldbetween a surface of the workpiece and a counter-electrode in thedeposition fluid.
 8. An apparatus for depositing nanotubes onto aworkpiece, comprising: a vessel configured to contain a deposition fluidhaving a plurality of nanotubes; a workpiece holder configured to hold asurface of the workpiece in a deposition zone relative to the vessel,wherein the workpiece holder has an electrical contact configured toprovide an electrical potential to the workpiece; a counter-electrode inthe vessel; and a nanotube separator in the vessel configured to sort afirst portion of the nanotubes from a second portion of the nanotubes.9. The apparatus of claim 8 wherein the nanotube separator comprises afield generator configured to generate an energy field in the depositionfluid that acts on the second portion of the nanotubes differently thanthe first portion of the nanotubes.
 10. The apparatus of claim 9 whereinthe field generator comprises a first separator electrode and a secondseparator electrode, and wherein the first and second separatorelectrodes are configured to contact the deposition fluid.
 11. Theapparatus of claim 9 wherein the field generator comprises anelectromagnet in the vessel.
 12. The apparatus of claim 9 wherein thefield generator is located at a sorting zone upstream from thedeposition zone relative to a flow of the deposition fluid through thevessel.
 13. The apparatus of claim 9 wherein the field generator islocated in the vessel.
 14. The apparatus of claim 8 wherein the nanotubeseparator comprises a filter in the vessel.
 15. The apparatus of claim14 wherein the filter comprises a mesh configured to filter out thesecond portion of the nanotubes from the first portion of the nanotubes.16. The apparatus of claim 8 wherein the nanotube separator comprises apatterned mask having openings through which the first portion of thenanotubes can pass to deposit the first portion of the nanotubes ontothe workpiece.
 17. The apparatus of claim 8 wherein the first portion ofthe nanotubes comprises first nanotubes having a first characteristicand the second portion of the nanotubes comprises second nanotubeshaving a second characteristic, and wherein the nanotube separatorcomprises a field generator configured to generate an energy field thatacts on the first nanotubes differently than the second nanotubes.